For cooling fired bulk material, for example cement clinker, reciprocating or travelling grate conveyor coolers are used in which the bed of the built material conveyed on the grate surface has a substantially constant bed height in the first cooling zone which serves for heat recovery.
The pressure loss of the cooling air stream passing through the material bed is made up of the resistance of the grate and the resistance of the granular mass of material. The pressure below the grate surface is essentially the pressure due to resistance to air flow. In the grate plates and in the granular mass of material. Thus the pressure measured below the grate surface characterises the pressure loss in the material mass. If the pressures in all the chambers in the longitudinal direction of the cooler are measured, this is designated as the pressure profile.
In the known method referred to above, in which the granular mass of material has a substantially constant bed height in the first cooling zone which serves for heat recovery, the pressure profile falls off in the transport direction. As more detailed investigations have shown, a pressure profile which falls off the material bed rises in the transport direction at least in the first cooling zone which serves for heat recover. At the beginning of the first cooling zone the layer height is low as is required for effective quenching of the hot bulk material to avoid caking together. As fired bulk material progresses through the first cooling zone serving for heat recovery, the bed height rises. The relatively long heat exchange time between gas and fired bulk material provides good heat recovery.
The fired bulk material cooling apparatus disclosed in the von Wedel patent increases the bed height in the transport direction. The increase in bed height is achieved by means of a baffle plate which projects down from above and into the material bed at the end of the first cooling zone and holds back the material in the first cooling zone. However, at the end of the first cooling zone the fired material is still at a relatively high temperature and possesses a high hardness and is abrasive. The baffle plate projecting into the granular mass of material is exposed to extraordinarily severe wear and consequently must be replaced after a comparatively short operating time necessitates very undesirable shutdown periods.